1. Field of the Invention
The present invention relates to a dynamic damper and a propeller shaft.
2. Description of the Related Art
There are dynamic dampers, which reduce vibration of an automobile driving power transmitting member, such as a propeller shaft, in order to reduce vehicle vibration and mechanical noise. Such dynamic dampers include an outer pipe, a weight disposed inside the outer pipe and an elastic body disposed between the outer pipe and the weight. This dynamic damper is pressed into a hollow shaft constituting the propeller shaft and is fixed thereto.
According to Japanese Utility Model Application Laid-Open No. H4-122843, the outer diameter of the outer pipe under its free state is larger than the inner diameter of the hollow shaft. A slit is provided in the outer pipe perpendicular to the circumferential direction thereof in order to improve ease of pressing the dynamic damper into the hollow shaft of the propeller shaft. Existence of this slit in the outer pipe enables the dynamic damper to be contracted elastically from the free state. Consequently, when the dynamic damper is pressed into the hollow shaft, the outer pipe is contracted from the free state so that the same dynamic damper can be engaged into the hollow shaft easily. After the dynamic damper is pressed into the hollow shaft, the outer pipe generates an elastic restoration force expanding the outer pipe to the free state, so that the outer pipe is fit to an inner face of the hollow shaft.
The conventional technology has the following problems.
(1) The outer pipe is always contracted due to the slit. Therefore, the outer pipe is contracted and deflected by vibration applied to the hollow shaft during use after it is pressed into the hollow pipe, thereby likely deteriorating the initial vibration resistance of the dynamic damper.
(2) To maintain an elastic restoration force for stably expanding the outer pipe from its contraction state to the free state, stiffness of the outer pipe needs to be secured. Therefore, the outer pipe needs to be provided with a thickness higher than a predetermined level. In this case, there is a possibility that within the range of such a limited inner diameter of the hollow shaft, the weight and the elastic body located within the outer pipe may not secure necessary volumes (diameter, thickness). Consequently, the weight of the dynamic damper is increased, thereby deteriorating the easiness of being pressed in.
An object of the present invention is to press a dynamic damper into a hollow shaft easily, which allows the damper to be fixed thereto stably, and which makes the dynamic damper compact.
According to the present invention, there is disclosed a dynamic damper comprising an outer pipe, a weight disposed inside the outer pipe and an elastic body interposed between the outer pipe and the weight.
The outer pipe contains at least one slit crossing the circumferential direction of the outer pipe, and the slit is filled with elastic filler.